///Document soumis, la révision doit encore être faite./// The CO2 post-combustion capture with amine solvents is modeled as a complex system interconnecting process energy consumption and solvent degradation and emission. Based on own experimental data, the kinetics of monoethanolamine degradation is included into a model of the CO2 capture process. The influences of operating conditions and flowsheet improvements on solvent loss and process energy requirement are quantified and validated with pilot plant data. Oxidative degradation in the absorber is identified as the major cause of solvent loss. On the contrary, thermal degradation does not appear as a major concern. Finally, this study leads to a decrease by 10% of the process exergy requirement along with a reduction by 11% of the solvent loss, all that by using a single model. Thus, this model provides a practical tool to minimize both the energy requirement and the solvent degradation by the design of large-scale CO2 capture units. [less ▲]

Production and purification of hydrophobin HFBII has recently been the subject of intensive research, but the yield of production needs to be further improved for a generic use of this molecule at ... [more ▼]

Production and purification of hydrophobin HFBII has recently been the subject of intensive research, but the yield of production needs to be further improved for a generic use of this molecule at industrial scale. In a first step, the influence of different carbon sources on the growth of Trichoderma reesei and the production of HFBII was investigated. The optimum productivity was obtained by using 40 g/L lactose. Carbon starvation and excretion of extracellular enzyme were determined as two main conditions for the production of HFBII. In the second phase, and according to the physiological mechanisms observed during the screening phase, a bioreactor set up has been designed and two modes of cultures have been investigated, i.e. the classical submerged fermentation and a fungal biofilm reactor. In this last set-up, the broth is continuously recirculated on a metal packing exhibiting a high specific surface. In this case, the fungal biomass was mainly attached to the metal packing, leading to a simplification of downstream processing scheme. More importantly, the HFBII concentration increased up to 48.6 ± 6.2 mg/L which was 1.8 times higher in this reactor configuration and faster than the submerged culture. X-ray tomography analysis shows that the biofilm overgrowth occurs when successive cultures are performed on the same packing. However, this phenomenon has no significant influence on the yield of HFBII, suggesting that this process could be operated in continuous mode. Protein hydrolysis during stationary phase was observed by MALDI-TOF analysis according to the removal of the last amino acid from the structure of HFBII after 48 h from the beginning of fermentation in biofilm reactor. Hopefully this modification does not lead to alternation of the main physicochemical properties of HFBII. [less ▲]

This work is a part of a project aiming at developing a renewable fuel for gasification purposes, through convective drying of sludge/wood mixtures. The first step consists of characterizing the behavior ... [more ▼]

This work is a part of a project aiming at developing a renewable fuel for gasification purposes, through convective drying of sludge/wood mixtures. The first step consists of characterizing the behavior of sawdust/sludge mixtures during the application of convective drying. The influence of the mixing step (no mixing against 30 s at 40 rpm), as well as the sawdust/sludge ratio (1/9, 2/8, 3/7 and 4/6 on a dry basis) and the effect of the drying temperature (50 °C, 80 °C and 110 °C) have been investigated. In this study, X-ray tomography, a non-invasive imaging technique, is used to assess changes in the volume, void and exchange surface at the beginning and the end of the drying process. Results first confirm the importance of the mixing step on the drying behavior: the drying rate of the mixed sludge is lower than that of the original sludge. Nevertheless the addition of sawdust is shown to have a positive impact on the drying process from a mass ratio of 2/8, with drying rates higher than that of the original sludge. With increasing amount of sawdust, the initial and final bed volumes, initial and final total exchange surfaces, and initial void fraction increase linearly, but the bed volume shrinkage and final void fraction decrease linearly. [less ▲]

Solvent degradation is a major drawback for the large-scale implementation of post-combustion CO2 capture due to amine consumption and emission of degradation products. In the present work, we refine a ... [more ▼]

Solvent degradation is a major drawback for the large-scale implementation of post-combustion CO2 capture due to amine consumption and emission of degradation products. In the present work, we refine a previous kinetic model for describing solvent oxidative and thermal degradation based on experimental results. The CO2 capture process is then modeled in Aspen Plus with assessment of solvent degradation. As a result, this work provides a useful tool for the identification of optimal operating conditions that minimize both the energy and environmental impacts of the process. [less ▲]

Single-use bioreactors have been increasingly used for animal cell cultures on microcarriers in screening experiments. Because of their manufacturing process, the shape of these kinds of vessels such as ... [more ▼]

Single-use bioreactors have been increasingly used for animal cell cultures on microcarriers in screening experiments. Because of their manufacturing process, the shape of these kinds of vessels such as the BIOSTAT® Cultibag STR one, is limited. For example, technical constraints on weld seams limit angles to 30° and no baffle may be installed. The shape of standard re-usable vessels may thus not be exactly reproduced and the flow structure may thus significantly differs from the flow structure in standard bioreactors. [less ▲]

Fungi are microorganisms exhibiting high secretive power of various metabolites and have the ability to perform post-translational modifications during protein synthesis. In the field of fermentation ... [more ▼]

Fungi are microorganisms exhibiting high secretive power of various metabolites and have the ability to perform post-translational modifications during protein synthesis. In the field of fermentation industry, they are ideal hosts for secondary metabolites and recombinant protein production. At the industrial-scale, equipments usually required for solid-state or submerged fermentation of filamentous fungi have demonstrated their limitations in terms of productivity, mass transfers or products recovery (1, 2). Recently, fungal biofilm reactors were designed to combine advantages from submerged and solid-state culture and reveal their usefulness for greater secondary metabolites production relative to submerged culture conditions (3). In our work, we propose the design of a fungal biofilm reactor for a recombinant protein production from an Aspergillus oryzae strain containing a GFP reporter gene system under the control of a promoter specifically induced in solid-state conditions. The fungal biofilm reactor is composed of a metal structured packing, having the function of inert support for biofilm growth, immerged or aspersed by a liquid medium. Whereas recombinant protein production is not significantly different at the flask-scale between submerged and biofilm conditions, productivity is higher in the submerged conditions at the bioreactor-scale. Presence of recombinant proteins entrapped in the biofilm matrix highlights a diffusion constraint and a lower mass transfer in our fungal biofilm reactor. However, persistence of a free liquid biomass of low viscosity and fungal biomass retention on the support are attractive for the implementation of a continuous process in our fungal biofilm reactor. Further studies will consider a 2-D proteomic comparison of the extracellular medium from fungal biofilm reactor and submerged culture conditions in order to better understand proteins secretion and identify over-expressed proteins in biofilm conditions. [less ▲]

Solvent degradation may be a major drawback for the large-scale implementation of post-combustion CO2 capture due to amine consumption and emission of degradation products. However, its influence on the ... [more ▼]

Solvent degradation may be a major drawback for the large-scale implementation of post-combustion CO2 capture due to amine consumption and emission of degradation products. However, its influence on the process operations has rarely been studied. In the present work, a kinetics model describing solvent oxidative and thermal degradation has been developed based on own experimental results for the benchmark solvent, i.e. 30 wt% monoethanolamine (MEA) in water. This model has been included into a global Aspen Plus model of the CO2 capture process. The selected process modelling approaches are described in the present work. Using the resulting simulation model, optimal operating conditions can be identified to minimize both the energy requirement and the solvent degradation in the process. This kind of process model assessing solvent degradation may contribute to the design of large-scale CO2 capture plants to consider not only the process energy penalty, but also its environmental penalty. Indeed, both aspects are relevant for the large-scale deployment of the CO2 capture technology. [less ▲]

This work is part of a project aiming at developing a renewable fuel for gasification purposes, through the convective drying of sludge/wood mixtures. The first step consists in characterizing the drying ... [more ▼]

This work is part of a project aiming at developing a renewable fuel for gasification purposes, through the convective drying of sludge/wood mixtures. The first step consists in characterizing the drying behaviour of sludge/sawdust mixtures, in a convective fixed bed dryer. The influence of the mixing step (no mixing against 30 s at 40 rpm) and the sawdust/sludge ratio (1/9, 2/8, 3/7 and 4/6 on a dry basis) was investigated. X-ray tomography, a non-invasive imaging technique, was used to assess changes in volume and exchange surface during drying. The sawdust addition was shown to have a positive impact on the drying process from mass ratio of 2/8. Results showed that the volume and exchange surface increased with higher sawdust addition during the whole drying process. Moreover, a linear decrease of the exchange surface is observed with sludge, while a plateau is reached after a linear phase for sludge/sawdust mixtures. As expected, the drying rate of sludges or sludge/sawdust mixtures decreased nearly linearly with the exchange surface. For sawdust/sludge mixtures, the drying rate continued to decrease after the end of shrinkage, due to internal transfer limitations. These promising results open the way to new valorisation ways, especially for very pasty sludge. [less ▲]

Convective drying of wastewater sludges and sawdust/sludge mixtures was studied. The first part of this work was an experimental study performed in a cross-flow convective dryer using 500 g of wet ... [more ▼]

Convective drying of wastewater sludges and sawdust/sludge mixtures was studied. The first part of this work was an experimental study performed in a cross-flow convective dryer using 500 g of wet material extruded through a disk with circular dies of 12 mm. The results showed that the sawdust addition has a positive impact on the drying process from a mass ratio of 2/8, on a dry basis, with observed drying rates higher than the original sludge. The second part of this work consisted of developing a drying model in order to identify the internal diffusion coefficient and convective mass transfer coefficient from the experimental data. A comparison was made between fitted drying curves, well represented by the Newton’s model, and the analytical solutions of the diffusion equation applied to a finite cylinder. Variations of dimensional characteristics such as the volume and exchange surface of the sample bed were obtained by X-ray tomography. This technique allowed confirm that shrinkage, which is an important phenomenon occurring during sludge and sawdust/mixture drying, must be taken into account. The results showed that both the internal diffusion coefficient and convective mass transfer coefficient were affected by mixing and sawdust addition. The internal diffusion coefficient changed from 7.77×10-9 m2/s for the original sludge to 7.01×10-9 m2/s for the mixed sludge and then increased to 8.35×10-9 m2/s for the mixture of a mass ratio of 4/6. The convective mass transfer coefficient changed from 9.70×10-8 m/s for the original sludge to 8.67×10-8 m/s for the mixed sludge and then increased to 12.09×10-8 m/s for the mixture of a mass ratio of 4/6. These results confirmed that sawdust addition was beneficial to the sludge drying process as the mass transfer efficiency between the air and material increased. Reinforcing the texture of sludge by adding sawdust can increase the drying rate and decrease the drying time, and then the heat energy supply will be reduced significantly. The study also showed that neglecting shrinkage phenomenon resulted in an overestimation for the internal diffusion coefficient for the convective drying of sludges and sawdust/sludge mixtures. [less ▲]

In most bioprocesses, it is fundamental to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. Computational Fluid Dynamics can ... [more ▼]

In most bioprocesses, it is fundamental to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. Computational Fluid Dynamics can provide detailed modeling about hydrodynamics and mixing. However, it is computationally intensive, especially when reactions are taken into account. Another way to predict hydrodynamics is the use of “Compartment” or “Network-of-zones” model which are much less demanding in computation time than CFD. However, compartments and fluxes between them are often defined by considering global quantities not representative of the flow complexity. To overcome the limitations of these two methods, a solution is to combine compartment modeling and CFD simulations. The aim of this study is to propose a compartment model where the flow rates between two adjacent compartments are easily computed from the velocity fields obtained by CFD. The mixing evolution predicted by the CFD-based compartment model have been then compared with mixing experiment results. Unlike a CFD mixing simulation and a classical compartment model, the CFD-based compartment model proposed in this work reproduces with a good accuracy the spatial distribution of concentrations during the mixing process and this, without any adjustable parameters. [less ▲]